Method of vulcanizing rubber and resulting products



Patented Nov. 5, i929 HENRY B. MORSEOF DANVERS, MASSACHUSETTS, ASSIGNOR,BY MESNE ASSIGNMENTS,

To ALBERT o. BUBRAGE, 3B,, or IPSWICH, MASSACHUSETTS Y METHOD OFVU'LCANIZING'RUBIBER AND RESULTING PRODUCTS No Drawing. Applicationfiled June 4,

This invention relates to the art of treating" rubber or rubbercompounds, and has for'an object the provision of an improved procedurefor'the vulcanization of the same in the presence of an accelerator andof compounds or compositions with which to effect the purpose of theinvention. I

In the'art of rubber manufacture, it has long been known that thevulcanizing process may be accelerated by the addition of va-.

7 may be mixed with the rubber or rubber compounds without inducingappreciable vulcanizing efiect at atmospheric temperature or duringmilling operations, but which activelyaccelerate the reaction in thecustomary vulcanizing treatment. Other accelerator compounds, frequentlytermed ultra accelerators or semi-ultra accelerators initiate thevulcanizing reaction sometimes prematurely, either in the cold ofilyorduring the mixing operation, resulting in scorching; which hinders orentirely prohibits the further use of the rubber or rubber compound.Consequently, such compounds ordinarily have not been used in themanufacture of rubber products, even though they would greatly reducethe time required for vulcanization and may be otherwise suitable foruse'in rubber compositions.

By the present invention it is foundthat 'theaccelerating action ofaccelerator compounds generally in rubber compositions, may be inhibited(at ordinary and slightly elevated temperatures'andf during the mixing1e29,. Swarm. 368,431.

and milling operations) or retarded by'the addltion of organlc compoundsof a certain type hereinafter defined, and that thereafter thevulcanizing reaction,-efiec ively accelerated by the accelerator,--n1aybe caused to proceed at will by subjecting the rubber composition to bevulcanized to vulcanizing conditions. v

It is thought that the accelerator andthe inhibitor react or combine toform a reaction product or compound which does not promote thevulcanizing reaction of the vulcanizable composition (under thepreliminary conditions such as mixing and milling) but which, under thevulcanizing conditions such; as increased temperature, dissociates andliberates the'accelerator which then actsin its accelerating capacity,and the inhibitor may remain inert or may itself act as an accelerator.

In other words, the critical temperature of the accelerator,'withrespecttoits initiating prematurely the vulcanizing reaction in therubber, is apparently raisedto a point above the temperatures of,milling or com canizing' treatment.

The compounds manifesting" such inhibiting action uponpremature'initiation of vulcanization by accelerators;- (and moreespecially the ultra accelerators and those sometimes referred to'as.semiultraaccelera torsamong which may be, mentioned the;

thiazoles, represented by mercapto benzo' thiazole, certain.disulphides'such as tetra;

methyl thiuram disuliplhide, certain mono sulphides such as tetraethyl'thiuramvmonosulphide, etc., and their derivatives) are found totypically include the nitrosoamines in which R and R represent alkyl oraryl radicals (or nuclei) which may be alike or unlike and in turn maycontain or be associated; with one or moresubstituents. v

For example, the aryl radicals or nuclei R and R', or either of them maycontain further substitutions, which are typically monovalent andreferably alkyl hydrocarbon radicals of whic the methyl group isrepresentative, as m in phenyl orthotolyl nitroso-amine.

In the representative example of the invention, rubber and the usualvulcanizing and filler materials, together with the desired amounts ofthe accelerator compound and inhibiting compound, may be compounded andmixed in the usual manner as by milling" (without prematurevulcanization or scorching), and subsequently molded and vulcan- .izedto the required degree of cure, by heating to the usual range ofvulcanization temperatures. The rate of vulcanization and degree of cureobtained may be accurately controlled by the time and temperature ofvulcanization,

to provide a'final cure equal to or better than that obtained withoutthe use of the preliminary inhibiting compound or-vprehibitor.

' In a relinnnary scorching test, for example, m which the compoundswere subjected to especially'high temperatures during the mixing and miling' operations unti scorching was effected, a rubber compositioncontaining:

100- parts rubber (smokedsheet) 3. parts sul hur' 5 parts Z115 partmercapt o benzo thiazole to which .43, art dibeta 'iiaphthylnitrosoamine was ad ed, was thoroughly milled and mixed on the mixingrolls; the mix was then removed and again milled on rolls, purposelyheated by steam so as to maintain a temperature in the stock ofapproximately 95 to 1009 C.,-fo

curred; A corresponding stock without the addition 'of dibeta naphthylnitroso-amine, upon beingmilled and like conditions 0 minutes. f r

Asimilar test carried out compound of the formula: a

temperature, searche in 100-partsrubber (smoked sheet) V 3 parts sul hura 5 parts'Zn v 15 part tetra meth lthiuram disulphide 7 5 part dibe napthyl nitroso-amiiie produced scorchin in 72 minutes." i er likeconditions the compound, wit out the rd'ibeta naphthyl'nitroso-amine,was

65 scorched in twenty minutes.

-'With addition of 0.75 partof r 110'minutes before scorching ocda nd agn-3 1 under I upon a rubber A third compound, having the formula thylthiuram monosulphide 75 part dibeta naphthyl nitroso-ainine was treatedin the same way as the preceding compounds and scorching took place in118 5 minutes, while the same compound, without 7 'dibeta naphthylnitroso-amine, was scorched in about 65 minutes, under the sameconditions. v

This test, developed for the purpose, serves to measure the-degree ofthe retarding or inhibiting effect of the-inhibiting com ound upon thevulcanization reaction and t e accelerating influence of the ultraaccelerator at temperatures of about C. or less, as con- 3 trasted withvulcanizing temperatures which as ordinarily employed are above 120 C.

' Similar tests were carried out employing the same composition, butwith a difierent lot of smoked sheet rubber which tended to scorchslower (without the addition of prehibitor) than the rubber emgeoyedabove. v The results obtained are given low:

Table I STOCK- Minutes before scorching Stock without prehibitorDiphenyl nitroso-amine 110 Dialpha Naphth lnitroso-amine 62 Phenyl betanap th lnitroso-amine- 93 Phenyl alpha napl t ylnitroso-amine 93Di-orthotol l nitroso-amine 97 Phenyl ort otolyl:nitroso-amine 102Phenyl paratolyl nitroso-amine 102 Benzyl phenyl nitroso-amine 52 sMethyl phenyl nitroso-amine 57 .Diethyl nitroso-amine 55 Piperidinenitroso-aminen 55 Garbazol nitroso-amine 46 In a typical application ofthein'vention to the usual vulcanizing procedure, rubber compounds wereprepared as follows:

. p I v I 100 parts rubber 40.5 parts'carbon black 5.0 parts zno 3.0parts sulphur 5.0 parts mineral rubber h 3.0 parts stearic acid I .8part mercapto benzo thiazole- 1 III Series, as indicated in-the abovelist in con- O nection wlth the scorching test. 3. Same as Formula Iwith addition of .75 The experimental results are presented 1n partdiphenyl IIItI'OSO-SJIIHIG. th f ll t bl IV Table III Same as Formula Iwith addition of .5Q A B C D part diphenyl mtroso-amine. These weremlxed by milling 1n the usual smokedsheets i 100 100' 100 100 manner,care being taken, especially with the gf gggflfigg g g g 2 compound ofFormula I, to prevent prehmig i w i g g g y nary vulcanlzation orscorching. The mixed Stezl ric 53121 -I 3 3 3 3 compounds were then laidn thin sheets 1n gg gggg mg g ggggf 8 a vulcamzlng mold and vulcanizedat 20 amine 0 0 Benzyl henyl n1tros0-am1ne 0 .0 0.75 0 pounds 7 steampressure. Samples of each Carbazofnitroso-amine 0 0 0 0.75 compound werevulcanlzed, for penods of 30, 45 and 60 minutes, respectlvely. One por-i=t1on of each sample was then Sub ected to a r Final Final tensilestrength test the results b8111 given tensile elongaa stoc 300% 500%lbs. per tion in II) the fOllOWlIlg table. Mi Pounds 7 sq. in. per centJ pressure v Table II 20 740 2010 3335 550 v 20 737 2110 3535 665 Cureat twenty pounds steam pressure 50 20 321 2200 3720 070 I 60 20 700 20203450 680 30 Minutes 75 20 843 2250 3550 070 75 20 880 2390 3910 665 7520 985 2600 4260 705 t l a] 75 20 850 2280 3700 650 300 5 91151 9 3 9020 930 2450 3300 550 P m 00 20 000 2500 3950 530 H Per cent 00 20 10032720 4110 540 00 050 2530 3050 050 I .32-.. A 735 1955 3400 685 n A 380)1140 2120 575 Table IV III A 583 l 1575 2030 550 IV A 537 1520 3100 535A B 0 D Smoked sheets- 100 100 100 100 45 Minutes Carbon black--- 40 4040 4 3 5 5 5 5 h 5 5 5 5 r10 1 Final g g g 300% 500% 1 5 5 5, 333%Mercapto benzo thgaiifu 0 3 0 3f 0.3 0.3

per cent, Dibeta naphthyl mtroso-aznme-.. 0 0 75 0 0 a 3 Phenyl betanaphthyl mtrosor Y amine 0 0 0.75 0

958 4050 I ifiiliefiffiiiiifii .fi fffff. 0 0 0 0.75 n 4 A 712 2000 3420050 t III A 243 2440 "4125 075 IV A 010 2500 4150 075 Cure Fius l {Finalh) BllSl e e onga- 4 v Mm Pounds 300% 500% 1:35 tionint I1. 0010111115 5Pramre q 1 I so I 20 005' 1005 3500 710 33 2 32 33 20 7 700 300% 500% -ptwnm 60 v 20 057 1005 3200 555 sq. in. per cent I 75 20 850 2200 3300700 75 20 867 2360 3850 650 1 .5. A 1105 2330 N 4050 040 7 75 20 0002355 3340 v665 D 75 20 540 2320 3750 355 II A 935 2550 4150 050 00 20040 2430 4000 075 111 A v 1135 2330 4175 5 535 00 20 035 2550 4075 555 I00 20 035 2500 4000 055 IV A 1120 2930 4.280 025 00 '20 970 2550 4000 5Sameas Formula I with addition of 1.0

part diphenyl nitroso-amine.

Similar vulcanizing experiments were carlike substituent groups, andhydrocarbon radicals of both the aliphatic and aromatic From the datathus obtained it is to, be bbserved that, not only are the rubber compounds prepared with an addition-ofthe canization or scorching, but thatwhen vulcanized at 20 pounds steam pressure and for the periods oftimeindicated, the vulcanized product exhibits as d or in some instancesa superlor. cure (wit respect to intermediate 65 and finalelongationyaluesy'than the coming' to the particular'conditions ofpractice and the characteristics desired-in the resultmg product, aswill be clear to those skilled in the art of treating rubber. I y 1 Thisapplication s: ac ntinuation in part of my application, Seri 1 No.323,556, filed December 3, 1928,.and is designated as case III-7 of agroup of continuation applications filed on even date herewith.

Iclaim:

1.- Method of vulcanizing rubber or rubber compositions with avulcamzing agent and an Table V 7 position to which such addition hasnot been ma e. L' Y A B Q D It istheiefore shown that by meansof thisinventlon not only may extremely active ac-' smoked sheets 100 1 0 100100. celerators WhlOh have been hitherto un- 5 Carbon black 40 -40 4o 40Mmmmbb, 5 5 5 5 ava11able for use in the rubber industry on g g g g g gaccount of their very hlgh activity) be safely Stem-i0 daiiinn ilimn 3'a 3- a employed 1n rubber compounds and mixed figiifggyfiifiii 8 g; gaand m lled Evithgut inritiatlng premature .vul-

lpel'l e111 USO-81111119-- 0 o w sseatrlasgtsz;zzzrsihu'ssaesir U ilarlyc0151 ounded .and vulcanized but without the a itibn of an inhibitin reaent Cure Y b g Fmal Final I .1s also mdlcated that whereas diaryl Smtensile elongm I 15 ck Pounds 500% lbs-W m m substltuted mtroso-aminesare es eclall ef- Mm ressum sq. in. per cent y r P a fectlve, withrespect to the prevention of prem 7 1870 I mature'acceleratlon'ofvulcanization, the al- 7 33 v 9,; 2132 $32 kyl or dlalkyl substltutedmtroso-amines may g gfg 23% 32 also be used, although somewhat lessefi'ective. g; Q Z82 313g 333g 33; Compounds which are in some respectsre '4; g fig} gag ggg lated to the subst tuted mtroso-amlnes above 90 2032 I 2440 defined, and have-been thus tested for use in :8 Egg gag Egggccoidanfie with the mfienfimmunclude car- 90 20 1120 2825 4120 630 azoe n1 roso-amme w )10 maybe spoken P0 of as mtroso N- carbazole,- v

TamevI 7 a B D N-NO Smoked sheets 1 g 1 g 1 a 5 5 5 5 Carbazolemtroso-amine or nitroso N-carg g g g bazole,-how ever, is not: strictlyin the same 35 Mempto bemothimle 3 3 3 3 category with the othercompounds tested 'Dialpha napmp 1nmosififiilil o 0175 0' o and in factshows but httle retardlng effect {52%;} f,} ,f, f::: 3 3 8- mthescorclnngtest. Thep1per1d1nen1troso-' amma hkevgse does not manlfestpronounced retar inge ects. The results are given, howo Cum i ever,because they are related to the other fifi J3, mtroso-ammo com ounds.Thelr failure to Stock 3 7 17 P Min Pounds :5: g 3 33 be more effectivein theserespects may be atpressure tr1buted to the valence linkagebetween the R I p 60 m 858 2250 I 3660 660 1; groups of zhemglllosg-amuie; vihilclh I w1 e apparen rom e ormu a o e 60. 20 770 21203620 680 g 33 31% $8 3 'former compound, as above given. I While theabove disclosure relates to a pregg g 3 g ferred procedure, accordmg tothe nvention, 15; -20 975 2420 man 610 and to s eclfic rea ents em 10 ed1 s eclfic 15 20 93a 430 4050 680 P y I} P p k proportions, 1t 1s to beunderstood that vane-- g 18:3 4 g2 tions may be'made in both the mode'of carryr g rose 51 40 o 3;; mg out the invention and in the nature andamountof the several reagents used, accord- 10 3. Method of vulcanizingrubber or rubber compositions with a Vulcanizing agent and an organicaccelerator characterized by controlling the action of the acceleratorwith phenyl orthotolyl nitroso-amine.

4. Method of vulcanizing rubber or rubber compositions with avulcanizing agent and a sulphur-containing organic acceleratorcharacterized by controlling the action of the accelerator with a diarylsubstituted nitroso amine containing a methyl radical in one of the arylnuclei.

5. Method of vulcanizing rubber or rubber compositions with avulcanizing agent and a sulphur-containing organic acceleratorcharacterized by controlling the action of the accelerator with an arylorthotolyl nitrosoamine.

6. Method of vulcanizing rubber or rubber compositions with aVulcanizing agent and a sulphur-containing organic acceleratorcharacterized by controlling the action of the accelerator withphenylorthotolyl nitrosoamine.

7. Method of vulacnizing rubber or rubber compositions with avulcanizing agent and an accelerator containing a thiazole nucleuscharacterized by controlling the action of the accelerator with a diarylsubstituted nitrosoamine containing a methyl radical in one of the arylnuclei.

8. Method of vulcanizing rubber or rubber compositions with avulcanizing agent and an accelerator containing a thiazole nucleuscharacterized by controlling the action of the accelerator with an arylorthotolyl nitrosoamine.

9. Method of vulcanizing rubber or rubber compositions with avulcanizing agent and an accelerator containing a thiazole nucleuscharacterized by controlling the action of the accelerator with phenylorthotolyl nitroso amine.

and mercapto benzo thiazole characterized by controlling the action ofthe accelerator with phenyl orthotolyl nitroso-amine.

13. An accelerator composition comprisingan organic accelerator and adiaryPsubstituted nitroso-amine characterized by containing amethyl'radical in one of the aryl nuclei.

14. An accelerator composition comprising an organic accelerator and anaryl orthoi tolyl nitroso-amine.

15. An accelerator composition comprising an organic accelerator andphenyl orthotolyl nitroso-amine.

16. An accelerator composition compris- I ing a sulphur-containingorganic accelerator and a diaryl substituted nitroso-amine characterizedby containing a methyl radical in one of the aryl nuclei.

17. An accelerator composition comprising a sulphur-containing organicaccelerator and an aryl orthotolyl nitroso-amine.

18. 'An accelerator composition comprising a sulphur-containing organicaccelerator and phenyl orthotolyl nitroso-amine.

19. An accelerator composition, comprising an accelerator containing athiazole nucleus and a diaryl substituted nitroso-amine characterized bycontaining a methyl radical in oneof the aryl nuclei.

20. An accelerator composition compris ing an accelerator containing athiazole nucleus'and an aryl orthotolyl nitroso-amine.

I 21. An accelerator composition comprising an accelerator containing athiazole nucleus and phenyl orthotolyl nitroso-amine.

22. An accelerator composition comprising mercapto benzo thiazole and adiaryl substituted nitroso-amine characterized by containing a methylradical in one of the aryl nuclei.-

23. An accelerator composition comprising mercapto benzo thiazole and anarylorthotolyl nitroso-amine. I

24. An accelerator composition comprising mercapto'benzo thiazole andphenyl orthotolyl nitroso-amine.

Signed by me at Boston, Massachusetts,:

this 1st day of June, 1929.

HENRY B. MORSE.

10. Method of vulcanizing rubber or rubber compositions with avulcanizing agent and mercapto benzo thiazole characterized bycontrolling the action of the accelerator with 4 a diaryl substitutednitroso-amine containing a methyl radical in one of the aryl nuclei. 11.Method of vulcanizing rubber or rub- 60 her compositions with avulcanizing a ent and mercapto benzo thiazole characterize b controllingthe action of the accelerator wit an aryl orthotolyl nitroso-amine.

12. Method of vulcanizing rubber or rub- 65 her compositions with avulcanizing agent

